Speed reducer recirculating cooling system

ABSTRACT

A closed recirculating air cooling system for a speed reducer having a plurality of gears disposed in a housing which comprises a dirven fan for withdrawing warm air from inside the housing, a cooling network for receiving and cooling the warm air, and duct means for conducting cooled air back into the housing. Provision may also be included for collecting oil entrapped in the air and returning it into the speed reducer housing.

nited States Patent [1 1 Wellauer 51 June 5, 1973 [54] SPEED REDUCER RECIRCULATING COOLING SYSTEM [75] Inventor: Edward J. Wellauer, Wauwatosa,

Wis.

[73] Assignee: The Falk Corporation, Milwaukee,

1 Wis.

[22] Filed: June 28, 1971 [21] Appl. N0.: 157,205

' [52] U.S. Cl ..74/606 A, 55/269, 184/107 [51] Int. Cl ..F16n 39/02 [58] Field of Search ..165/47, 106, 107;

[56] References Cited UNITED STATES PATENTS 2,990,443 6/1961 Camilli ..174/15 R 2,391,186 12/1945 Noble ..74/606 A 2,947,798 8/1960 Camilli et a1 ..174/15 R 2,419,439 4/1947 Cook 2,654,583 10/1953 Treanor ..165/107 FOREIGN PATENTS OR APPLICATIONS 344,703 3/1931 Great Britain ..74/606A 115,797 7/1926 Switzerland ..165/107 Primary Examiner-Manuel A. Antonakas Att0rneyDOnald G. Casser and Thomas W.

Ehrmann [57] ABSTRACT A closed recirculating air cooling system for a speed reducer having a plurality of gears disposed in a housing which comprises a dirven fan for withdrawing warm air from inside the housing, a cooling network for receiving and cooling the warm air, and duct means for conducting cooled air back into the housing. Provision may also be included for collecting oil entrapped in the air and returning it into the speed reducer housing.

3 Claims, 7 Drawing Figures PATENTEUJUH 5 I975 3,736,812

SHEET 1 OF 2 /3 E /4 INVENTOR /5 EDWARD J.WELLAUER ATTORNEY PATENTEDJUH 5mm 3,736,812

SHEET 2 OF 2 Fig.4

INVENTOR EDWARD J.WELLAUER AT TOFINI Y SPEED REDUCER RECIRCULATING COOLING SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to a closed recirculating air cooling system for speed reducers which is adapted to remove air from a speed reducer housing, cool it and return the cooled air to the housing.

2. Description of the Prior Art Even though gear type speed reducers normally have a specified rated mechanical horsepower, the mechanical horsepower rating is not the factor limiting the amount of load for reducers of this type that are to be run continuously for relatively long periods of time. In

stead, the reducers also have a thermal horsepower rating which indicates the horsepower that may be transmitted by a reducer without undue overheating. A variety of cooling systems have been designed for gear type speed reducers to overcome problems of overheating, several of which employ air to provide the desired cooling. For example, US. Pat. No. 3,406,591 employs a fan that draws air into one end of a shroud enclosing the top portion of a gear housing. The air circulates past the upper portion of the housing and exits at the opposite end of the shroud. US. Pat. No. 3,353,591 discloses a gear unit having exterior cooling ribs and a suction blower. Cool air is drawn by the suction blower and is directed by deflector plates to circulate past the cooling ribs.

The above described systems provide a certain amount of cooling, but they are not especially efficient since they depend on indirect cooling and a large amount of air must be continuously circulated through the systems to maintain their cooling effect.

In my copending application Ser. No. 157,206 entitled Speed Reducer Internal Cooling System and filed on the same date herewith, a cooling system is disclosed that consists of an air blower attached to one end of a reducer housing and an air vent formed in the opposite end of the housing. Cool air is blown into the housing and hot air is forced out through the vent. This type of system provides efficient cooling, but it was not designed to operate with reducers that normally have a large amount of lubricating oil vapor entrained in the air inside the housing because the oil vapor would naturally be vented out of the housing with the hot air. Thus, not only would the lubricating oil supply continually be deplenished, but in addition the oil vapor would be vented into the atmosphere to cause innumerable problems.

SUMMARY OF THE INVENTION The present invention provides a closed recirculating cooling system for a gear type speed reducer with gears that are mounted on shafts and are enclosed in a housing. The cooling system includes several suction ports formed in a wall of the housing. A driven fan is connected to the exterior surface of the wall to overlie the suction ports and is enclosed by a cover that is hermetically sealed to the housing. A first air duct provides communication between the interior of the fan cover and one end of a heat exchanger and a second air duct is communicatively interposed between the opposite end of the heat exchanger and an opening in a wall of the housing. The fan draws hot air out of the housing through the suction ports and circulates the air to the heat exchanger through the first air duct. As the hot air is passed through the heat exchanger, cooling fins cause the air temperature to be lowered and the cooled air is returned to the housing via the second air duct.

The main objects of this invention are to provide a highly efficient cooling system for a gear reducer to increase the load capacity of the reducer; to provide a cooling system for a gear type speed reducer that cools warm air from within the reducer housing by circulating it through a heat exchanger and then transmits this cooled air back into the housing to directly come in contact with the gears of the reducer; and to provide a closed cooling system whereby lubricating vapor suspended in the air that is drawn from within the housing to be cooled will not be permanently removed from the housing but will be condensed as the air is cooled and returned back to the housing. A more limited object is to provide the particular structures hereinafter claimed.

By the implementation of this invention, one of the primary advantages achieved is that the cooled air will directly come in contact with the gears and the circulating bulk oil as well as mist and spray in the speed reducer to provide more efficient gear cooling than that previously achieved by other cooling methods.

Still another area where the closed air cooling system will be effective is in certain applications where the natural heat-dissipating qualities of the speed reducer will be restricted when the unit is housed in an enclosure of sound-absorption material to create an acoustic barrier.

The foregoing and other objects and advantages of the invention will appear from the following description. In the description reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration and not of limitation a preferred embodiment of the invention. Such embodiment does not represent the full scope of the invention, but rather the invention may be employed in a variety of embodiments, and reference is made to the claims herein for interpreting the breadth of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of a gear type speed reducer with a first embodiment of the cooling system of the present invention incorporated therewith;

FIG. 2 is a plan view of the speed reducer and cooling system of FIG. 1;

FIG. 3 is a cross sectional view of the speed reducer and cooling system of FIG. 1 taken along the plane 3-3 and showing a fan of the cooling system disposed on a shaft of the reducer;

FIG. 4 is a cross sectional view of a heat exchanger comprising a part of the cooling system of FIG. 1 taken along the plane 4-4;

FIG. 5 is a fragmentary view with parts in section of a second embodiment of the present invention showing the cooling system fan disposed on the shaft of an electric motor;

FIG. 6 is a side elevation view of a second type of heat exchanger that may be utilized in the present invention; and

FIG. 7 is a cross sectional view of the heat exchanger of FIG. 6 taken along the plane 7-7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a gear type speed reducer incorporating a presently preferred embodiment of the present invention, the reducer including a housing 1 that encloses the gears of the reducer. The present invention is particularly suited to be utilized with speed reducers that normally have a large amount of lubricating oil vapor entrained in the air within the reducer housing 1. The oil vapor has the dual functions of providing lubrication for the gears of the reducer and also providing a certain amount of gear cooling. The housing 1 comprises an upper section 2 and a lower section 3. The bottom portion of the lower section 3 serves as a sump in which lubricating oil for the operating components of the reducer is stored, which oil level is represented by a dotted line 4. The internal components of the reducer are shown in the cross section view of FIG. 3. An input shaft 5 and an output shaft 6 are journaled at opposite ends in sidewalls 7 and 8 of the housing 1. A high speed drive gear 9 is disposed on the input shaft 5 and a low speed driven gear 10 is similarly disposed on the output shaft 6 to form a single reduction unit. The speed reducer construction forms no part of the pres ent invention, which is not restricted to use with the illustrated type of unit as it would work equally well in conjunction with other forms of gear type speed reducers.

Also shown in FIG. 3 is a suction fan 11 that forms part of the present invention. The fan 11 is mounted on one end 12 of the input shaft 5, so that the fan is driven by the input shaft. Suction ports 13 are formed in the sidewall 8 of the housing 1 near the end 12 of the input shaft 5 and it is through the ports 13 that the vapor ladened hot air is withdrawn from inside the housing 1 by the fan 11.

Referring again to FIG. 1, it can be seen that the suction ports 13 are preferably formed in the side wall 8 to symmetrically surround the input shaft 5 in order that the suction fan 11 overlies the suction ports 13. Secured to the sidewall 8 of the housing 1, as by bolts 14, is a cover 15 that encloses the fan 11 and is hermetically sealed to the sidewall 8. The cover 15 acts as a pocket into which the hot air from the housing 1 is drawn by the fan 11. The cover 15 has a spout 16 that leads to a cooling network consisting of a first air duct 17, a heat exchanger 18 and a second air duct 19. As hot air is continually sucked through the suction ports 13 into the pocket formed by the cover 15, air is forced through the spout 16 of the cover 15 into the first air duct 17 which leads to the heat exchanger 18. Although some cooling is realized as the hot air passes through the first air duct 17, the primary cooling of the hot air is accomplished as the air passes through the heat exchanger 18 to the second air duct 19 that leads back into the housing 1 through an inlet port 20 in an endwall 21 of the housing 1.

The heat exchanger 18, as shown in FIGS. 1 and 2, consists of a substantially cylindrical chamber 22 with an inlet port 23 and an outlet port 24 in which an end' of the first air duct 17 and an end of the second air duct 19 are respectively disposed. Medially positioned between the two ports 23 and 24 is the primary cooling apparatus of the exchanger. As shown in FIG. 4 the cooling apparatus lies crosswise in the chamber 22 of the exchanger 18 and consists of a metal fluid tube 25 on which a plurality of cooling fins 26 are affixed. The tube 25 has an inlet end 27 and an outlet end 28 that protrude through the cylindrical wall 29 of the chamber 22 and between the two ends 27 and 28 the tube 25 winds up and down in a sinuous fashion inside the chamber 22. Preferably, cool water is circulated through the fluid tube 25 to cool the fins 26. When the hot air passes through the exchanger 18, the air comes in contact with the fluid tube 25 and the cooling fins 26 whereupon heat from the air is conducted to the water circulating through the fluid tube 25 and the hot air is consequently cooled.

As the air is cooled in the exchanger 18 the oil vapor originally entrained in the air condenses to form droplets of oil that are too heavy to be carried by the air flow. If these oil droplets are not returned to the reducer housing 1 there would be a significant reduction in the lubricating oil stored in the housing 1, which would then have to be continually replenished. This loss of oil is prevented in the present invention by the provision of an oil return line 30 that extends from the bottom of the exchanger 18 into the upper section 2 of the reducer housing 1 to provide communication between the interiors of the exchanger 18 and the reducer housing 1.

FIG. 5 illustrates another embodiment wherein the fan 11 of the cooling system is driven by an electric motor 31 attached to the cover 15, instead of being driven by a shaft of the speed reducer. An electric motor driven fan is particularly useful in maintaining proper direction of air flow and fan speed regardless of the direction of rotation and speed of the pinion shaft 5. Although the use of the water cooled exchanger 18 as described is presently preferred, this invention may be employed in conjunction with other types of heat exchangers that act to cool air that is circulated through them. FIGS. 6 and 7 illustrate a second type of exchanger 32 for use with the present invention that comprises a chamber 33 which is similar to that of the exchanger 18. Disposed inside the chamber 33 is a cooling apparatus comprising a plurality of fins 34 that extend substantially the length of the chamber 33. The fins 34 resemble narrow ridges which are each positioned lengthwise on the outer surface of a cylinder. The cooling produced by the exchanger 32 depends on the transmission of heat from the hot air to the fins 34 through conduction but since there is no cooling water to convey the heat from the exchanger 32 as is provided in the exchanger 18, the heat is transmitted to the wall 35 of the chamber 33 and is radiated away from the exchanger 32. Again an oil return line 36 is utilized with the exchanger 32 to convey the oil droplets that form in the exchanger 32 back into the reducer housing 1. In a similar fashion the cool air exiting from the exchanger 32 passes through the second air duct 19 and into the housing 1 to come in direct contact with the reducer gears.

There has thus been described a cooling system which provides an improved method for cooling the gears within a reducer housing. Through the employment of the cover 5 and the first air duct 17 which are illustrated as forming a first conduit means, the air is drawn out of the housing 1 by the fan 1 l and conveyed to the heat exchanger 18. While circulating through the heat exchan'ger18, the air is cooled by cooling apparatus within the exchanger 18 and it is then conveyed back into the housing 1 through a second conduit means which is illustrated in the first embodiment as a second air duct 19. In this way air from within the housing is constantly being cooled and returned to the housing to provide direct cooling for the gears disposed in the housing.

Although several specific examples of this invention have been herein described in order to illustrate the invention, it is expected that changes can be made in the described embodiments and that other embodiments can be designed by those skilled in the art which will remain within the true spirit and scope of this invention.

I claim:

1. In a speed reducer of the type having a plurality of gears disposed on several shafts in a housing having a lower portion that contains a lubricating fluid, and at least one of said shafts is an input shaft and at least one of said shafts is an output shaft, a closed recirculating cooling system comprising, in combination:

a suction port formed in a wall of the housing of the speed reducer;

suction means mounted to overlie the suction port and draw air out of the housing through the suction port;

enclosure means that fits over the suction means and is hermetically sealed to the housing wall; external heat exchanging means for cooling air; first conduit means for conveying air from the enclosure means to the heat exchanger;

second conduit means for conveying air from the heat exchanger into the housing; and

an oil return line that communicates between the heat exchanger and the housing to return condensed oil from the heat exchanger into the housing.

2. The combination of claim 1 wherein the suction means is mounted on one end of the input shaft of the speed reducer and is driven by said input shaft.

3. The combination of claim 1 further including a motor mounted on the enclosure means, and arranged to drive the suction means. 

1. In a speed reducer of the type having a plurality of gears disposed on several shafts in a housing having a lower portion that contains a lubricating fluid, and at least one of said shafts is an input shaft and at least one of said shafts is an output shaft, a closed recirculating cooling system comprising, in combination: a suction port formed in a wall of the housing of the speed reducer; suction means mounted to overlie the suction port and draw air out of the housing through the suction port; enclosure means that fits over the suction means and is hermetically sealed to the housing wall; external heat exchanging means for cooling air; first conduit means for conveying air from the enclosure means to the heat exchanger; second conduit means for conveying air from the heat exchanger into the housing; and an oil return line that communicates between the heat exchanger and the housing to return condensed oil frOm the heat exchanger into the housing.
 2. The combination of claim 1 wherein the suction means is mounted on one end of the input shaft of the speed reducer and is driven by said input shaft.
 3. The combination of claim 1 further including a motor mounted on the enclosure means, and arranged to drive the suction means. 